Gale Warning 452, NWS Anchorage, AK

957 
FZAK61 PAFC 052341
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
341 PM AKDT Sat Sep 5 2020

Offshore waters forecast for the Gulf of Alaska West of 144W

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ399-061415-
341 PM AKDT Sat Sep 5 2020
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

High pressure lingers over the northern Gulf through Sat night. 
A strong front moves into the western Gulf Sat night, then slowly
moves into the northern Gulf through Mon afternoon.

$$

PKZ351-061415-
Gulf of Alaska Offshore North of 57N and West of 144W-
341 PM AKDT Sat Sep 5 2020

.TONIGHT...E wind 10 to 20 kt. Seas 3 to 6 ft.
.SUN...E wind 15 to 30 kt. Seas 5 to 10 ft.
.SUN NIGHT...SE wind 30 kt. Seas 8 to 13 ft. Rain.
.MON...SW wind 20 kt. Seas 11 ft.
.MON NIGHT...SW wind 10 to 20 kt. Seas 11 ft.
.TUE THROUGH THU...W wind up to 20 kt. Seas 6 to 10 ft.

$$

PKZ352-061415-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
341 PM AKDT Sat Sep 5 2020

...GALE WARNING TONIGHT...

.TONIGHT...E wind 20 to 35 kt becoming SE 15 to 25 kt after
midnight. Seas 5 to 10 ft.
.SUN...SE wind 15 to 30 kt. Seas 6 to 11 ft. Rain.
.SUN NIGHT...S wind 20 to 30 kt. Seas 8 to 12 ft.
.MON...SW wind 15 to 25 kt. Seas 12 ft.
.MON NIGHT...SW wind up to 20 kt. Seas 7 to 12 ft.
.TUE THROUGH THU...S wind up to 20 kt. Seas 4 to 9 ft.

$$

707 
FZAK61 PAFC 061105
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
305 AM AKDT Sun Sep 6 2020

Offshore waters forecast for the Gulf of Alaska West of 144W

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ399-070115-
305 AM AKDT Sun Sep 6 2020
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A front moves into the western Gulf Sun morning, then slowly 
moves into the northern Gulf through Mon afternoon.

$$

PKZ351-070115-
Gulf of Alaska Offshore North of 57N and West of 144W-
305 AM AKDT Sun Sep 6 2020

...GALE WARNING TONIGHT...

.TODAY...E wind 15 to 30 kt. Seas 5 to 10 ft.
.TONIGHT...S wind 25 to 35 kt. Seas 8 to 14 ft. Rain.
.MON...SW wind 10 to 20 kt. Seas 11 ft.
.MON NIGHT...SW wind up to 15 kt. Seas 8 to 11 ft.
.TUE...S wind up to 20 kt. Seas 6 to 10 ft.
.WED THROUGH THU...W wind 10 to 20 kt. Seas 5 to 8 ft.

$$

PKZ352-070115-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
305 AM AKDT Sun Sep 6 2020

.TODAY...SE wind 15 to 30 kt. Seas 8 to 13 ft. Rain.
.TONIGHT...S wind 20 to 30 kt. Seas 8 to 12 ft.
.MON...SW wind 10 to 20 kt. Seas 12 ft.
.MON NIGHT...SW wind up to 20 kt. Seas 10 ft.
.TUE...SW wind 10 to 20 kt. Seas 6 to 10 ft.
.WED THROUGH THU...NW wind up to 20 kt. Seas 3 to 8 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 PM AKDT Fri Sep 4 2020

.ANALYSIS AND UPPER LEVELS...

A dissipating upper trough is allowing for widespread marginal
upper level instability over much of Southern Alaska, particularly
Southcentral. With afternoon heating, a few isolated thunderstorms
are possible, and a few formed earlier this morning south of
Cordova. Otherwise, the coverage of showers today has been much
less than previous days, due to the upper level instability
weakening with time. A number of locations, including Kenai,
Kodiak, Gulkana, and Koliganek all dipped into the 30s this
morning, with Kenai reaching the freezing mark for a brief time.
High pressure is over Southwest Alaska, allowing for patchy fog,
such as King Salmon saw this morning, and some persistent low
stratus over the Kuskokwim Delta. A large low over the western
Bering is nearly stationary, with no significant impacts other
than the usual cloudy, rainy and windy conditions.

&&

.MODEL DISCUSSION...

Model agreement is very good for the short term period. The
biggest struggle has been how they handle a developing Pacific
low as it approaches the Alaska Peninsula on Saturday. Previous
days' model runs have dissipated this compact but strong low much
more quickly, before the center reaches the AKPEN. Now the model
consensus keeps the low going until it reaches the AKPEN, then
quickly dissipating. Forecast changes today involve increasing
the expected winds and waves in this area from Kodiak Island
west. Forecast confidence is much higher than previous days.
Turnagain Arm and higher elevations winds was a point of focus
for the Southcentral forecast for Sunday through Monday with
the next storm that will impact the area.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

A fairly benign synoptic weather pattern will continue this
evening through Saturday. However, due to the more diurnal heating
today from less cloud cover and a fairly unstable atmosphere,
isolated thunderstorms are expected in Prince William Sound, the
western Kenai Peninsula, portions of the Susitna Valley and Copper
Basin. GOES-17 Day Cloud Phase Distinction RGB shows the strongest
convection currently in the western Copper Basin along the base of
the Talkeetna Mountains. Patchy radiational fog is likely along
the western Kenai Peninsula tonight due to less clouds expected,
light winds combined with persistence forecasting as fog was
observed last night.

A mild and sunny day is expected for Southcentral on Saturday as
transient high pressure extends across the region. High
temperatures are expected to remain in the low to middle 60s (F)
for the Anchorage Bowl, Matanuska and Susitna Valleys as well as
the western Kenai Peninsula.

A large fairly deep low will track northward across the eastern
Bering Sea Sunday through Sunday night. This will result in
widespread rain and wind across the Gulf waters and Southcentral,
as both the frontal system and an atmospheric river impact the
region. In particular, the track of this low is favorable for
strong winds along Turnagain Arm and the Anchorage Hillside, with
good potential for some of these winds to spread across much of
the remainder of Anchorage. This pattern also favors strong winds
through the Knik River Valley and across Palmer/Wasilla as well as
along the Copper River and through Glennallen. There is still
some uncertainty in the exact track of the low, which will impact
how strong the winds will get. However, it appears the peak of the
winds will be sometime Sunday night through early Monday morning.

Southwesterly flow aloft, abundant moisture transport in the form
of an atmospheric river, and strong dynamic forcing will lead to
widespread moderate to heavy rain Sunday evening through Monday
morning. The heaviest rain will be areas enhanced by southerly
upslope flow, including the Susitna Valley and Prince William
Sound. The heavy rain will not be long lasting, which should
minimize the threat of flooding. However, rivers in the Susitna
Valley are running high from rains of the past 10 days, so will
have to keep a close eye on flooding potential there. The lowest
rainfall amounts are expected in the Copper Basin as the Copper
Basin is located in the lee of the Chugach Mountains where
significant downsloping is expected.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

An upper level ridge of high pressure remains over Southwest
Alaska through early Saturday afternoon. As a result, mostly
sunny to partly cloudy conditions are expected through Saturday
afternoon. There is the threat for patchy fog in and around the
King Salmon area as well as around the Aniak area for early
Saturday morning. Any fog is expected to be brief between 5-9 am
Saturday morning before mixing out making way for more sunshine.
A strengthening storm system currently over the North Pacific is
beginning its trek northward. This system will send a front
through Southwest Alaska beginning Saturday afternoon with
increasing clouds from south to north. Northernmost areas will
be last to see the cloud cover increase. The best chance for any
showers with this first frontal system will be across the western
Alaska Range and the Kuskokwim Mountains due to upslope flow
against the mountains. Areas to the west of the Alaska Range but
east of the Kuskokwim Mountains will experience downsloping which
will aid in drying the column of air Saturday evening into Sunday.
However, a shower or two still cannot be ruled out.

The second system will be the one with more energy with it as well
as a stronger push of warmer and moister air for Sunday. As a
result, Sunday looks much wetter and windier for much of Southwest
Alaska. As of now it appears the steadiest rain is expected to
fall across the Kuskokwim Delta first beginning Sunday morning and
continuing through Sunday afternoon. While Bristol Bay and the
Middle Kuskokwim Valley may see rain showers Sunday the steadiest
and heaviest is expected late Sunday afternoon through early
Monday morning as the flow turns more southerly. As the front
moves through Sunday, expect stronger winds through Kamishak Gap
with sustained winds between 25-35 mph and gusts 45-60 mph as the
pressure gradient increases.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A low pressure system currently spinning northeast of Shemya will
continue retrograding (when a system moves from east to west) and
weakening through tonight. Small craft winds will continue to
occur on either side of this low through early Sunday morning
before diminishing further. Areas of rain will also continue to
occur across the western Aleutian Chain as this low moves
southwestward.

The next storm system of note is currently strengthening over the
North Pacific. This low will continue strengthening up till the
point it is about to enter the coastal marine zone south of Sand
Point. Expect this storm system to bring storm force winds and
gusts to much of the marine area south of Sand Point as well as
periods of rain beginning Saturday morning. As this low approaches,
clouds and winds will increase overnight into Saturday morning.
The strongest winds are expected Saturday morning through Saturday
evening south of the AKPEN. A second piece of energy will then
phase with the energy from the aforementioned low that will aid
in a second low pressure area developing late Saturday into
Sunday. Gale force winds are expected for areas north of the AKPEN
with storm force wind gusts beginning Saturday afternoon with the
gale force winds expected into the northern Bering Sea through
early Monday.

With increasing winds, the waves will also be on the rise south of
the AKPEN beginning Saturday morning. Waves will start around 6-8
ft building to 25-30 ft by Saturday afternoon as the strongest
winds move through. Waves will diminish gradually south of the
AKPEN Saturday evening. Additionally, waves will begin to increase
north of the AKPEN across the Bering and Bristol Bay Saturday
afternoon with wave heights of 7-11ft building to 15-20 ft by
Saturday night. Expect the increased wave heights Sunday across
the northern to central Bering with wave heights of 13-17ft.
Waves heights and winds will begin to gradually come down Monday
afternoon/evening as the storm system weakens and continues moving
northward.

&&

.MARINE (Days 3 through 5/Monday through Wednesday)...

A well-developed low over the eastern Bering Sea will exit
northward along the coast of western Alaska Monday through
Monday night. Widespread gales will be in place to start the day,
but winds will diminish through the period. Another smaller and
weaker low will enter the western Bering and Aleutians Monday
night into Tuesday. There is some uncertainty in depth and track
of this low. Expect at least small craft winds with some potential
for Gale force winds along the western Aleutians Tuesday through
Wednesday.

For the Gulf of Alaska waters, the effects of the Bering system
will linger through Monday, with a gale force front pushing
onshore along the north Gulf coast and Prince William Sound.
Conditions then look quieter until Wednesday when there is
potential for small craft or gale westerlies across the western
Gulf, though confidence is low.

&&

.LONG TERM FORECAST (Days 4 through 7/Monday through
Thursday)...

An active and generally wet pattern will continue through Wednesday
with a broad low over the Bering Sea moving up into the Norton
Sound by Monday evening. Models are in reasonable agreement that
the bulk of the heaviest precip associated with an occluded front
will end from SW to NE on Monday with showery/breezy conditions
likely lingering in the southwest and interior through at least
Wednesday morning. There is good model agreement that strong
southwest flow will continue towards the AKPEN/Southcentral until
midweek with several rounds of rainfall possible near the Prince
William Sound region. However, 12z guidance suggests the
"atmospheric river" event and associated moisture may be most
impactful closer to the AK Panhandle where the highest QPFs are
currently projected. Some model inconsistencies with this feature
remain, so this may need to be reevaluated for future updates.

The tap should firmly shut off to close out the week as the
longwave trough over the Bering Sea breaks down and as the
prominent Northeast Pacific ridge retreats into the the western
CONUS by Thursday. Much quieter and clearer conditions are fairly
likely region-wide Thursday-Friday as a "fair weather" ridge
develops along the Bering coast. Current solutions do lean towards
another wave developing near the AKPEN by Friday evening, so the
respite in the stormy fall pattern may be short lived.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 155.
		 Gale Warning 150 160 165 172 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...ED/SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MV
MARINE/LONG TERM...MK/AS/SB